Installing Barrel Extension Question

[MG42fan]

Ok I was searching and didn't find anything on this. So I'll ask.

I got a barrel to replace the drilled barrel from my parts kit. Is there anything I need to know about installing the barrel extension on the new barrel? Something extra I may need to do to do it right or do I just go for it?

[JBaum]

Headspace is determined by the joint of the barrel and extension. Screw it together, check headspace. If incorrect, screw some more/less until it's right.

[MG42fan]

How do I keep it from unscrewing during operation after proper headspacing is achieved? Weld? Locktite? Or nothing extra needed?

Update: I also noticed something else I need to take note on. Head spacing gauges for 8mm mauser have two different degrees. Old degree is 20 degree, new SAMMI degree is 19 degree.

I have Yugo barrels. What degree should they be, 19 or 20? That way I can get the proper gauges. Gauge company said 19 can appear longer in a 20 degree chamber. Gauge company makes both degrees.

[Boondoggle]

The barrel is staked to the extension to prevent turning.

[MG42fan]

I see. So how do I remove the old barrel extension from the drilled barrel without tearing things up?

Anybody have an answer for the go gauge set and field gauge question?

[JBaum]

Generally speaking, it's a whole lot less trouble to pay $150 for a usable barrel than to screw around with the barrel extension, but since you're already there.....

Clamp the barrel in a big vise, unscrew the extension with an appropriately sized wrench. Heat if necessary. Drill out the peen if necessary. Twist (warp) the barrel extension and it's scrap, so be careful.

[amafrank]

Also be aware that headspace gauges for bolt action rifle use will be on the tight side for a machinegun. Use the gauge for the older type since the yugo's built the guns back in the 50's and 60's not yesterday. You want the thing to lock up on the go and not on the field. Skip the no-go. If you make the headspace too tight the gun will likely have issues running. This is advice only for the machinegun....if you have a semi than make it tight. To set the headspace screw the barrel and extension together as tight as they will go and check. If its loose than turn a couple thousandths off the flange on the barrel and try again. If its tight you can make up shims from shim stock but they must be full circle rings in order to make sure the barrel is properly attached. You cannot simply drop a couple pieces of shim stock in. Once you get your headspace correct you can use red loctite on a semi or peen the joint in a real gun. The semi won't normally get as hot as a real MG42 since you can't fire it at 1300rpm. The chamber end of the barrel is the cold end and even a red hot barrel can be handled by the extension if you're careful.
One other thing to consider is that different ammo will have different reactions to headspace. A gun set up to work with original WWII german ammo will tear off case heads of french ammo made in the 50's because the french set the shoulders back more than normal. Get your headspace set close and test fire. If you're getting rings from loose headspace tighten it up a little. If the gun won't lockup then loosen a bit. As noted in an earlier thread buying another barrel will save you time and probably money if you can't do the work yourself.
Frank

[MG42fan]

Generally speaking, it's a whole lot less trouble to pay $150 for a usable barrel than to screw around with the barrel extension, but since you're already there.....

Clamp the barrel in a big vise, unscrew the extension with an appropriately sized wrench. Heat if necessary. Drill out the peen if necessary. Twist (warp) the barrel extension and it's scrap, so be careful.

So any idea how to remove the barrel extension without warping it?

Thanks ama.

[JBaum]

Clamp the barrel in a big vise, unscrew the extension with an appropriately sized wrench. Heat if necessary. Drill out the peen if necessary.